Multiple alarm system



Se t. 9, 1969 R. COLMAN MULTIPLE ALARM SYSTEM Filed March 1, 1966 1 vdi-I N VENTOR.

fbseer Com/w MULTIPLE ALARM SYSTEM Robert Colman, New York, N.Y.,assignor to General Alarm Corporation, New York, N .Y., a corporation ofDelaware Filed Mar. 1, 1966, Ser. No. 531,000 Int. Cl. G08b 19/00, 3/10U.S. Cl. 340-384 21 Claims ABSTRACT OF THE DISCLOSURE Multipleacoustical alarm system for producing different types of alarm signalsaccording to occurrence of different conditions, including free runningtone signal generator for producing signals at audible basic frequency,free running control generator connected to shift output frequency oftone signal generator at subaudible basic frequency, and switch andcontrol means arranged in connection with said generators to establishdifferent basic frequency combinations according to manner in whichswitch means are operated.

This invention relates to acoustical alarms and more particularly itconcerns an electrically operated multiple alarm system.

The present invention is particularly useful as a multipurpose alarmarrangement which can be activated by any of several types ofdisturbance. For example, it is often beneficial to provide an alarmwhich will sound not only in response to an attempted burglary but whichwill also sound in response to the pressing of an emergency or doorbellbutton, and which further will sound in response to the presence of fireor excessive heat.

It is important to identify by various sounds the different conditionswhich produce actuation of the alarm. Thus, a bell sound could indicatethe pressing of a doorbell or emergency button, while a buzzer or hornsound could indicate the occurrence of a fire, and a siren sound couldindicate the occurrence of an attempted burglary.

In the past, it was necessary to provide a different sound producingmechanism for each of the several types of alarm sounds sought to beproduced. These multiple mechanisms, even those of the electricalvariety, were expensive and bulky; and they required rather large powersources.

The present invention overcomes all of these difiiculties. According tothe present invention there is provided, in a single package, a novelalarm system which operates to produce various types of alarm soundsincluding bells, buzzers or horns, and sirens. This novel alarm systemrequires very little power; and it may be made extremely small, so smallin fact, that the entire system, including the power supply, may bemounted as a self contained unit on a door or other closure.

In an illustrative embodiment, the alarm system of the present inventionprovides different alarm sounds in response to different situationswhich may take place at a doorway. The system, which is completelypackaged in a single self contained unit is attached to a door. The unitis interconnected with a doorbell button, a thermostatic heat detector,and a force sensitive switch means. Operation of any of these elementswill cause the system to emit a diiferent type of sound at a highvolume. Thus, the doorbell button, when pushed, causes the system toring in the manner of a doorbell. The thermostatic heat detector on theother hand, when actuated by excessive heat, will cause the system tobuzz or sound as a horn. Further, the force sensitive switch means, whenoperated, will cause "the system to emit a siren sound. This sirensound, as will be seen, is especially United States Patent 3,466,649Patented Sept. 9, 1969 effective in calling attention to an attemptedbreaking into the closure, for it varies in frequency in a particularmanner which conveys and maintains a sense of urgency.

The present invention achieves the above described results by means of anovel circuit arrangement including a free running or astable tonesignal generator having an audible basic frequency. There isadditionally provided a free running control generator which isconnected to shift the output frequency of the tone signal generator ata subaudible basic frequency. Switch means are arranged in connectionwith the generators to establish diiferent basic frequency combinationsaccording to the manner in which the switch means are operated.Transducer means, such as a loudspeaker, is connected to convert theoutput of the tone signal generator to acoustical signals.

As illustratively embodied, the tone signal generator comprises anastable multivibrator circuit including a pair of transistors, withcross coupled time delay circuits. The control generator comprises aresistance-capacitance time delay circuit and a voltage responsivebreakdown means, such as a unijunction transistor or the equivalentthereof, connected to produce a recurrent sawtooth waveform. Means areprovided to couple the time delay circuits of the multivibrator into thecontrol generator so that the time delay action of the timing circuitsis varied by the impedance changes which occur during the operation ofthe control generator. The coupling means additionally includesswitching means which introduce different basic impedances between thecontrol generator and the tone signal generator to change the basicfrequencies of each of these generators.

The switching means, according to another aspect of the invention,serves to change the output of the control generator so that theimpedance changes produced by it will follow either a rectangular pulseor a sawtooth Waveform pattern according to the operation of theswitching means. By properly controlling the operation of the switchingmeans, the system can be made to produce an insistent siren type sound,a ringing bell sound or a born or buzzer sound.

According to a still further aspect of the invention, the switchingmeans can be arranged additionally to shift the symmetry, or duty cycleof the astable signal generator so as to simulate more realisticallycertain tones.

There has thus been outlined rather broadly the more important featuresof the invention in order that the detailed description thereof thatfollows may be better understood, and in order that the presentcontribution to the art may be better appreciated. There are, of course,additional features of the invention that will be described hereinafterand which will form the subject of the claims appended hereto. Thoseskilled in the art will appreciate that the conception upon which thisdisclosure is based may readily be utilized as a basis for the designingof other structures for carrying out the several purposes of theinvention. It is important, therefore, that the claims be regarded asincluding such equivalent constructions as do not depart from the spiritand scope of the invention.

Specific embodiments of the invention have been chosen for purposes ofillustration and description, and are shown in the accompanyingdrawings, forming a part of the specification, wherein:

FIG. 1 is a fragmentary perspective view illustrating one embodiment ofthe present invention arranged in conjunction with an entranceway;

FIG. 2 is a circuit diagram and schematic mechanical representation ofthe embodiment of FIG. 1; together with illustrative waveforms shown atselected locations throughout the system; and

FIG. 3 is an electrical schematic illustrating a modification of oneportion of the circuit of FIG. 2.

The entranceway shown in FIG. 1 includes a door which is mounted in theusual manner by means of hinges 12 to one side of a door casing 14. Thedoor 10 is provided with a conventional latch mechanism (not shown)which secures the door in closed position as shown and which is releasedupon turning a knob 16, so that the door can be opened.

A multiple alarm unit 18, forming one embodiment of the presentinvention, is mounted on the inside surface of the door 10 just abovethe knob 16. The multiple alarm unit 18, as shown, takes the form of asmall rectangular box and is completely self contained except forcertain external mechanical connections to be described.

As shown in FIG. 1 there is provided a chain lock plate on the casing 14in close relation to the alarm unit 18. A locking chain 22 may beengaged at one end to the plate 20. The other end of the chain 22 isaifixed to a chain anchor 24 on the multiple alarm unit 18. The plate20, the chain 22 and the anchor 24 cooperate to provide a chain lockmechanism which, when engaged, permits the door 10 to be openedslightly, but which prevents further opening movement of the door.

A door bell button 26 is mounted on the outside surface of the door 10and is connected mechanically to switching means within the multiplealarm unit 18 in a manner to be described.

There is additionally provided a bi-metallic thermostatic element 28which is mounted inside the multiple alarm unit 18. The element 28 isarranged to bend in response to the surrounding temperature exceedingcertain prescribed limits, and thus to actuate certain switching meansin the system.

The multiple alarm unit 18, as will be described becomes actuated inresponse to either (a) excessive tension on the locking chain 22, (b)pressing of the doorbell button 26, or (c) bending of the bi-metallicthermostatic element 28. Each of these situations will cause themultiple alarm unit 18 to emit a different type of sound. That is,excessive tension on the locking chain 22 will cause the unit 18 to emita siren sound having a particularly urgent characteristic; the pressingof the doorbell button 26 will cause the unit 18 to emit a ringing bellsound; and the bending of the bi-metallic thermostatic element 28 willcause the unit 18 to emit a horn or buzzer sound. Thus, the single unit18 will respond in difierent ways to different situations, thus enablinga person in the vicinity immediately to assess the particular situationbased upon the type of sound he hears without having first to go to thedoorway to see what has caused the disturbance.

As represented in the diagram of FIG. 2, the electrical circuits makingup the multiple alarm unit 18 are divided by means of heavy dashed linesA and B into three sep arate sections in which are containedrespectively a control generator 30, a tone generator 32, and a powerand output circuit 34. Each of the sections is supplied by a commonpositive voltage supply line 36 and a common negative voltage supplyline 38. These supply lines extend through the system from batteries 40located in the power and output circuit 34. A normally opened mainswitch 42 is positioned in series with the batteries 40 and serves toconnect them with the positive voltage supply line 36. The normallyopened switch 42 may be closed in various ways as will be explained morefully hereinafter.

The control generator 30 includes a uni-junction transistor 44 havingone base terminal connected to the negative voltage supply line 38 andthe other base terminal connected via a uni-junction resistor 46 to thepositive voltage supply line 36. A sweep generator circuit is also provided in the control generator section 30. This sweep generator circuitcomprises a sweep resistor 48 and a sweep capacitor 50 connected inseries between the positive and negative voltage supply lines 36 and 38.The emitter terminal of the uni-junction terminal transistor 44 isconnected to a junction point 52 between the sweep resistor 48 and thesweep capacitor 50.

A single-pole-double-throw bell switch 54 is arranged to move between afirst position, connected as shown to the junction point 52, and asecond position connected to a bell line 56 extending from a junctionpoint 58 between the uni-junction resistor 46 and the uni-junctiontransistor 44. The output of the bell switch S4 is connected to themovable element of a single-pole-double-throw horn switch 60 which ismovable between a first position con nected to a bypass line 62 and asecond position connected to one end of a variable impedance resistor64. The opposite ends of the bypass line 62 and of the variableimpedance resistor 64 are each connected to a tone control line 66 whichis coupled into the carrier generator 32.

The tone generator 32 includes an astable or free running multi-vibratorcircuit shown generally at 33. This circuit includes first and secondmulti-vibrator transistors 68 and 70 of the NPN variety. The emitters ofthese two transistors are each connected to the negative voltage supplyline 38 while their collectors are connected via associated collectorresistors 72 and 74 to the positive voltage supply line 36. Themultivibrator transistors 68 and 70 are cross coupled between theircollectors and bases by means of time delay circuits. These time delaycircuits include timing capacitors 76 and 78 connected respectivelybetween the base of one transistor and the collector of the othertransistors. The timing circuits each further include a timing resistor80 and 82 which extends between an associated transistor base terminaland the tone control line 66. The tone control line 66 thus forms aportion of each of the time delay circuits. It will be noted that thisline is connected through the control generator 30 to the positivevoltage supply line 36. Operation of the control generator 30 serves tovary the impedance between the tone control line 66 and the voltagesupply line 36. This in turn affects the operating characteristics ofthe timing circuits and thereby controls the output frequency of themultivibrator circuit 33.

There is additionally provided a variable duty cycle capacitor 84 and anormally opened duty cycle switch 86 in parallel with the timingcapacitor 78.

Output signals from the multivibrator circuit 33 are taken from thecollector terminal of the second transistor 70, and supplied via aseries connected coupling capacitor 88 and a shunt connected outputresistor 90 to the base terminal of a power output transistor 92 in thepower and output circuit 34. The power output transistor 92 is of thePNP variety and has its emitter terminal connected to the positivevoltage and supply line and its collector terminal connected in serieswith a loudspeaker 94 to the negative voltage supply line 38. Thus, theelectrical undulations produced in the tone generator 32 are amplifiedand converted to corresponding acoustical signals.

As shown schematically, the doorbell button 26 is connected to the bellswitch 54, the horn switch 60, and the normally opened main switch 42.The bi-metallic thermostatic element 28, in turn, is connected to thehorn switch 60, the duty cycle switch 86 and the normally opened mainswitch 42. The chain anchor 34, on the other hand, is connected only tothe normally opened main switch 42.

Actuation of either the doorbell button 26, the bimetallic thermostaticelement 28, or the chain anchor 24 will cause the various switches towhich they are connected to move from their shown unactuated positionsto their actuated positions. While the various connections between thevarious switches and the actuating elements are indicated to bemechanical it will readily be recognized by those skilled in the artthat equivalent electronic or electrical means such as siliconcontrolled rectifiers and the like may be substituted to effect theswitching action in response to actuation of the various elements.

Operation of the above described system is initiated upon closing of thenormally opened main switch 42 which effectively places the batteries 40in circuit across the positive and negative voltage supply lines 36 and38. When this occurs the control generator 30 and the tone generator 32goes into operation at a certain basic frequency and with a certain waveform characteristic, the frequency and wave form characteristic beingestablished by the particular condition of the various switches in theseelements at the time the normally opened main switch is closed. Thecombination of the waveforms and operating frequencies of these twoelements will establish the nature of the sound emitted at theloudspeaker 94.

The basic operation of the tone generator 32 is the same as that of anordinary multivibrator. That is, the first and second multi-vibratortransistors 68 and 70 conduct during alternate periods, and theinitiation of conduction of either of them causes an immediateextinction of the current flowing through the other thus terminating itsconduction. The duration of conduction of each transistor lasts onlylong enough for a charge to be rebuilt across its respective timingcapacitor 76 or 78. When this occurs, the voltage bias at the baseterminal of the nonconducting transistor then reaches a level suflicientto bring the transistor into conduction. This in turn causes the voltagelevel at the base terminal of the other transistor to be immediatelyreduced below the cut off point of that transistor. This alternateconduction proceeds at a rate established by the capacitance value ofthe timing capacitors 76 and 78 and amount of impedance which exsistsbetween each transistors base terminal and the positive voltage supplyline 36. This, as indicated previously, is varied during operation ofthe control generator 30.

The manner in which the control generator section 30 operates to varythe timing action of the multivibrator 33 is as follows: In order forthe timing capacitors 76 and 78 to achieve a sufficient charge to eifectswitching of their respective multi-vibrator transistors 68 and 70, itis necessary for current to fiowtinto these capacitors via theirrespective timing resistors 80 and 82. This current is obtained from thetone control line 66 which ultimately is connected through the controlgenerator 30 to the positive voltage supply line 36. The controlgenerator 30 varies the impedance between the positive voltage supplyline 36 and the tone control line 66 and thus varies the rate at whichthe timing capacitors 76 and 78 achieve their respective charges aftereach occurrence of transistor switching. Thus, the variations inimpedance produced by the control generator serve to control thefrequency produced by the tone generator 32.

During operation of the control generator 30, current flows from thepositive voltage supply line 36, through the sweep resistor 48 and intothe sweep capacitor 50 so that the voltage at the junction point 52gradually increases in magnitude. The rate at which this voltageincrease takes place depends, of course, upon the resistance andcapacitance values of these two elements. When the voltage at thejunction point 52 exceeds a given threshold level, depending upon theparticular characteristics of the unijunction transistor 44, a breakdownoccurs which drastically reduces the impedance between the emitter andlower base terminals of the transistor 44 so that the sweep capacitor 50discharges immediately via the transistor 44 to the negative voltagesupply line 38. When the capacitor 50 has discharged, the emitter tobase impedance of the unijunction transistor 44 is immediatelyreestablished and current flowing down through the sweep resistor 48 isagain directed into the sweep capacitor 50 so that the capacitor beginsto recharge at a relatively slow rate. As illustrated in the waveformdiagram (a), the voltage at the junction point 52 thus follows asawtooth pattern, rising relatively gradually to a given threshold leveland then dropping abruptly to a lower level. The rate or frequency atwhich this occurs depends of course upon the respective values of thesweep resistor 48 and the sweep capacitor 50 and also upon the thresholdor break down voltage of the unijunction transistor 44. For purposes ofthe present invention, the frequency rate is set to a sub-audible level.

OPERATION AS A SIREN ALARM As stated above, operation of the alarm unit18 to provide a siren effect occurs when excessive tension is producedupon the locking chain 22. Because of the connection between the chainanchor 24 and the normally opened main switch 42, the switch 42 isclosed upon excessive pull upon the locking chain 22. This places avoltage across the positive and negative voltage supply lines 36 and 38thus placing both the control generator 30 and the carrier generator 32into operation. During this time, the bell switch 54, the horn switch 60and the duty cycle switch 86 remain in their positions as shown in thediagram. Thus, the tone control line 66 is connected through the bypasline 62, to the junction point 52. As a result, the sawtooth voltagefluctuations at that junction provide corresponding impedancefluctuations to the tone control line 66. This, in turn, in cooperationwith the low impedance path through the bypass line 62, and the variousother system parameters serves to cause the multi-vibrator to oscillatebetween about 1200 and about 1800 cycles per second. This variation, ofcourse, follows a sawtooth pattern, as illustrated by the waveform andtakes place at less than 1 cycle per second. The resulting acousticalsignal produced at the loudspeaker 94'is a siren sound which varies insuch a manner that a special sense of urgency is conveyed. Moreover, ithas been found that this sense of urgency does not diminish with time,since it is not a type of sound which is easily accommodated by thehuman ear.

OPERATION AS A HORN ALARM Operation of the system as a horn alarm isinitiated by the bending of the bi-metallic thermostatic element 28 inresponse to the ambient temperature exceeding a glven preset value, suchas would occur as a result of a fire in the vicinity of the door. Whenthe element 28 bends, it causes the normally opened main switch 42 andthe duty cycle switch 86 both to close, and it further causes switchingof the horn switch 60. When this occurs, the batteries 40 becomeconnected across the positive and negative voltage supply lines 36 and38 as above described so that the control generator 30 and the tonegenerator 32 are placed into operation. The switching of the horn switch60 in the control generator 30 has the effect of placing the variableimpedance resistor 64 into circult between the tone control line 66 andthe positive voltage supply line 36. The result of this added impedanceis that it effectively increases the operating frequency of the controlgenerator 30 and simultaneously decreases the basic operationalfrequency of the tone generator 32. The parameters or values of thevarious elements in the control generator section 30 and tone generator32 are such that the imposition of the variable impedance resistor 64results in an increase in the control generator frequency toapproximately 30 cycles per second and a decrease in the basic operatingfrequency of the tone generator 32 to between 400 and 600 cycles persecond. The resulting signal output causes the loadspeaker 94 to emit adeep throated horn type sound of considerable volume.

The quality and authenticity of the horn sound is improved by theclosing of the duty cycle switch 86. This places the duty cyclecapacitor 84 into the timing circuit connected to the base terminal ofthe first multivibrator transistor 68, and effectively changes thetiming characteristics on one side of the multi-vibrator so that onetransistor conducts for a greater length of time than the other. Thischanges the duty cycle of the multi-vi brator circuit and serves toenhance the horn type sound produced by the system.

7 OPERATION AS A BELL ALARM When the doorbell button 26 is pressed, itcloses the main switch 42 and at the same time switches the position ofthe bell switch 54 and the horn switch 60. As indicated previously,closing of the main switch 42 operates to connect the batteries 40across the positive and negative supply lines 36 and 38 so that thecontrol generator 30 and the tone generator 32 are placed in operation.The variation in impedance between the carrier frequency control line 66and the positive voltage supply line 36 however does not follow thesawtooth waveform which occurs at the junction point 52 in the controlgenerator 30. Instead, the bell switch 54 places the tone control line66 into communication with the bell line 56 and thus with the junction58 between the junction resistor 46 and the uni-junction transistor 44.As shown in the waveform (b), the impedance variation produced by thisconnection follows a square wave pattern. As a result of this, the tonegenerator is shocked into different operating conditions as theimpedance on the tone control line 66 is abruptly changed. This suddenshocking of a resonant member, such as the tone generator 32, from onecondition to the other, simulates the striking of a bell; and in facthas been found to produce a bell sound at the loudspeaker 94. Thequality of the bell sound is improved by the simultaneous operation ofthe horn switch 60 to place the variable impedance resistor 64 intocircuit between the control generator 30 and the tone generator 32. Aswith operation as a horn, bell sounds are rendered more authentic bythis operation since it simultaneously increases the basic operatingfrequency of the control generator 30 and decreases the basic operatingfrequency of the tone generator 32. The variable impedance resistor 64and the variable duty cycle capacitor 86 are both shown to beadjustable. Means may be provided to factory set the values of theseelements to obtain a particular tonal quality for operation both as ahorn and as a bell, or, if desired, any of several well known means maybe provided for allowing the user to make his own adjustments inaccordance with his individual needs or desires.

As regards the other elements of the system, the following values haveprovided an especially satisfactory arrangement:

Unijunction resistor 46 ohms 1.2K Sweep resistor 48 do 3.0K Collectorresistors 72, 74 do 1.0K Timing resistors 80, 82 do 12.0K Outputresistor 90 do 1.2K Variable impedance resistor 64 (variable) 5.0K Sweepcapacitor 50 mfd 100 Timing capacitors 76, 78 pf 47,000 Couplingcapacitor 88 mfd l Unijunction transistor 44 2N2646 Multivibratortransistors 68, 70 2N1308 Batteries 40 volts 6 Loudspeaker 94 ohms 8FIG. 3 shows a modification of the control generator 30 wherein a PNPtype transistor 100, an NPN type transistor 102, and a diode 104 aresubstituted for the unijunction transistor 44; and an added resistor 106is connected between the uni-junction resistor 46 and the negativevoltage supply line 38. The base of the PNP transistor 100 is connectedto a junction between the resistors 46 and 106, and its emitter isconnected to the junction point 52 between sweep resistor 48 and thesweep capacitor 50. When the junction point voltage causes the base toemitter potential of the PNP transistor 100 to rise above its cut-offpoint, the transistor begins to conduct and allow current to flowthrough the diode 104 and a collector connected resistor 108 to thenegative voltage supply line 38. The base of the NPN transistor 102 isconnected to the emitter of the PNP transistor 100 and thus experiencesa voltage increase when the PNP transistor begins to conduct. Thecollector and emitter of the NPN transistor 102 are connected betweenthe junction point 52 and the negative voltage supply line 38; so thatwhen the base terminal potential is raised above cut-off, the transistor102 immediately allows the sweep capacitor to discharge.

The action thus produced by the two transistor arrangement is thus thesame as that produced by the unijunction transistor arrangement of FIG.2. In some situations the two transistor arrangement is more economicalin spite of the fact that it requires more elements, since the elementsused are more conventional and may be produced at a lower cost.

The following values for the various elements in the two transistorarrangement of FIG. 3 have been found to give satisfactory performancewith a system whose elements otherwise have the values tabulated above:

Added resistor 106 ohms 4.7 Sweep resistor 48 do 3.3K Collectorconnector resistor 108 do 470 PNP transistor 2N461 NPN transistor 1022N1308 Diode 104 1N461 It will be appreciated that the system of thepresent invention, while employing a minimum of elements, is extremelyversatile and is capable of responding to any of several situations orconditions. The elements used in the system moreover may be packed verycompactly so that the entire unit may be incorporated in a very smallcontainer. Moreover, the solid state elements used in this systemrequire very low driving power so that small penlight type batteries maybe packaged with the system to make a completely independent selfsupporting unit which can be mounted at locations remote from availableelectrical power sources.

What is claimed and desired to be secured by Letters Patent is:

1. A multiple acoustical alarm system for producing different types ofalarm signals according to the occurrence of different conditions, saidsystem comprising a tone signal generator for generating electricalsignals which vary at an audible rate, transducer means for convertingsaid electrical signals to corresponding acoustical signals, a controlgenerator for controlling the output frequency of said tone signalgenerator, said control generator being operable to vary at a basicfrequency, and according to a given wave pattern, the output frequencyof said tone signal generator, switch means arranged in circuit withsaid tone signal generator and said control generator to cause saidgenerators to operate at different basic frequencies according to thecondition of said switch means, said switch means being arranged tochange the basic frequencies of said generators in mutually oppositedirections, and means for operating said switch means according to acondition to be repre sented whereby said system produces a differentcharacteristic sound for each condition to be represented.

2. An alarm system as in claim 1 wherein said switch means furtherincludes means for switching said control generator in a manner toproduce control signals of different Waveshapes.

3. An alarm system as in claim 1 wherein said switch means furtherincludes means for changing the operational symmetry of said tone signalgenerator.

4. A multiple acoustical alarm system for producing different types ofalarm signals according to the occurrence of different conditionscomprising, a tone signal generator including an astable multivibratorcircuit having cross coupled timing circuits, and having a basicoperational frequency within the audible range, a free running controlgenerator having a basic operational frequency below the audible range,said control generator including variable impedance means arranged to beconnected into said timing circuits of said tone signal generator forchanging the output frequency of said tone signal generator inaccordance with the operation of said control generator, a plurality ofcoupling means having different fixed impedance characteristics, atleast one of said coupling means being constructed to simultaneouslyvary the basic frequencies of said tone signal generator and saidcontrol generator, switch means operable to connect dilferent ones ofsaid coupling means between said control generator and said timingcircuits according to different conditions to be indicated, whereby thebasic operational frequencies of said tone signal generator and saidcontrol generator are established by the existence or absence of saidconditions, and transducer means for producing acoustical signals inresponse to output signals from said tone signal generator.

5. An alarm system as in claim 4 wherein said control signal generatorincludes a sweep voltage charging circuit and a voltage responsivetrigger discharge circuit.

6. An alarm system as in claim 5 wherein said switch means includesmeans for switching said coupling means alternately between said sweepvoltage charging circuit and said trigger discharge circuit.

7. An alarm system as in claim 4 wherein said switch means includesmeans for changing the relative timing characteristic of said timingcircuits.

8. An alarm system as in claim 5 wherein said switch means is operablein response to a first condition to connect a first impedance couplingmeans between said timing circuits and said sweep voltage chargingcircuit, and is operable in a second condition to connect a secondimpedance coupling means, higher than said first impedance couplingmeans, between said timing circuits and said sweep voltage chargingcircuit, and is operable in a third condition to connect a thirdimpedance coupling means, higher than said first impedance couplingmeans, between said timing circuits and said trigger discharge circuits.

9. An alarm system as in claim 8 wherein said switch means is furtheroperable in response to said second condition to change the timingcharacteristic of one of said timing circuits with respect to the other.

10. A multiple acoustical alarm system comprising a tone signalgenerator including a pair of transistors, a pair of associated timedelay circuits cross coupled between said transistors to form an astablemultivibrator circuit having a basic output frequency within the audiblerange, a free running solid-state control generator having a basicoperational frequency below the audible range, coupling meansinterconnecting said control generator and said time delay circuits in amanner such that the basic output frequency of said tone signalgenerator is modulated with the basic frequency of said controlgenerator, said coupling means including means for switching its basicimpedance between discrete values for changing the basic operationalfrequencies of said multivibrator circuit and said control generator,and loudspeaker means connected to be driven in accordance with outputsignals from said multivibrator circuit and to generate correspondingacoustical signals.

11. An alarm system as in claim 10 wherein said time delay circuitsinclude means for changing the time delay characteristic of one circuitwith respect to the other, said last mentioned means being operable bysaid switch means.

12. An alarm system as in claim 10 where said time delay circuitsinclude capacitors and resistors connected via a common impedance pathto a voltage source, said common impedance path including said couplingmeans and at least a portion of said control generator.

13. An alarm system as in claim 12 wherein said coupling means includesa plurality of alternate paths of different impedances, said paths beingselectively connectable into said common impedance path by saidswitching means.

14. An alarm system as in claim 10 wherein said control generatorcomprises a resistor and a capacitor connected in series betweenpositive and negative voltage supply lines and a threshold voltageresponsive capacitor.

discharge means connected across said capacitor for effectivelydischarging same.

15. An alarm system as in claim 14 wherein said discharge means includesresistance means connected between said positive and negative voltagesupply lines and a first junction along said resistance means whichundergoes a square wave pattern during operation of said controlgenerator while a second junction between said resistor and saidcapacitor undergoes a sawtooth wave pattern, said switching meansfurther being operative to switch said coupling means alternatelybetween said first and second junctions.

16. In a multiple acoustical alarm system the combination of a tonesignal generator whose basic output frequency varies within the audiblerange in response to applied control generator outputs, a controlgenerator having an output frequency below the audible range, couplingmeans including a plurality of impedance elements constructed to beconnected between the output of said control generator and the input ofsaid tone signal generator, both said tone signal generator and saidcontrol generators being constructed to have their basic frequencydependent upon the impedance through said coupling means, said couplingmeans including switch means operative to produce changes in theimpedance value of said coupling means in response to various conditionsto be indicated thus to shift the basic frequency of both of saidgenerators, and transducer means connected to the output of said tonesignal generator for producing acoustical signals in response to outputsfrom said tone signal generator.

17. An alarm system as in claim 16 wherein the output frequency of saidtone signal generator varies in response to variations in the outputimpedance of said control generator.

18. An indicator alarm system for indicating the nature of disturbanceto a closure, said system comprising a tone signal generator forgenerating electrical signals having frequencies within the audio range,said tone signal generator being constructed to produce, in a quiescentstate, electrical signals which vary at a basic frequency, transducermeans for converting said electrical signals to corresponding acousticalsignals, a control generator arranged to shift the output frequency ofsaid tone signal generator, said control generator itself having asubaudible basic frequency, impedance means and plural switch meanscoupling said tone generator and said control generator in such mannerthat different combinations of the states of such switch means changesthe impedance to cause said generators to operate at different basicfrequencies, a plurality of disturbance sensing devices each responsiveto a different disturbance at said closure, and means connecting saiddisturbance sensing devices to said switch means in a manner such thateach of said sensing devices responds to a different disturbance byproducing a different combination of states of said switch means.

19. An indicator alarm system according to claim 18 wherein said controlgenerator is operable to vary a basic frequency of said tone signalgenerator such that at the occurrence of a first given disturbance, thecharacteristic sound at said transducer means corresponds to a siren.

20. An indicator alarm system according to claim 18 wherein said controlgenerator is operable to vary a basic frequency of said tone signalgenerator such that at the occurrence of a second given disturbance thecharacteristic sound at said transducer means corresponds to a bell.

21. An indicator alarm system according to claim 18 wherein said controlgenerator is operable to vary a basic frequency of said tone signalgenerator such that at the occurrence of a third given disturbance thechar- OTHER REFERENCES acteristic sound at said transducer meanscorresponds to Ho: Variable Frequency Square Pulse Gengration, a hornElectronic Engineering, December 1963, pp. 822-823.

References Cited Kyle: Electronic Sirens, Electronics World, April 1964,

UNITED STATES PATENTS 5 P113243 2,455,472 12/1948 Curl et a1. 179-1715JOHN W, CALDWELL, Primary Examiner 3,196,432 7/1965 Kock 3403843,114,114 12/1963 Atherton et aL 331 111 CHARLES M. MARMELSTEIN,Assistant Examiner 3,183,454 5/1965 Streit 331113 10 US. Cl. X.R.

3,210,686 10/1965 Rocca 331111 33147,52

